i love-hate how clueless kamitani and ryuuichi are when it comes to girls oh my god. kamit...

I think Kamitani is aware but just doesn't care, and yeah Ryuuichi is a lost cause for now. Maybe he'll become a bit more aware once his brother have grown up a little and depends less on him, but for now most of his brain and emotional power is spent in taking care of Kotaro (and the other kids) and academics, as learning how to fit in more and more in his new family.